1. Field of the Invention
The present invention relates to a method of assembling an air bearing which is applied to a machine tool and to measuring equipment, and float-supports a slider, on the moving side, so as to be able to move relative to a guide on the fixed side, and relates also to the air bearing and to a linear drive unit equipped with the same.
2. Description of the Related Art
Conventionally, an air bearing equipped with a slider float-supported so as to be able to move relative to a guide, disclosed Japanese Unexamined Patent Publications 08-28565 (JP-A-08-28565), is shown in FIG. 8. The air bearing 100, that is shown in FIG. 8, includes a guide 101 formed bearing surfaces 101a on two opposing surfaces thereof, and a slider 103 that has opposing surfaces 103a opposed to the bearing surfaces 101a via bearing gaps 102 and is float-supported by the guide 103 so as to be able to linearly move.
The slider 103 has flow paths 104 for supplying pressurized gas (compressed air) to the bearing gaps 102. Upon supplying the pressurized gas into the bearing gaps 102 through the flow paths 104, the slider 103 is float-supported. The size d of the bearing gaps 102 formed over and under the guide 101 is selected to be several microns to several tens of microns. Therefore, the guide 101 and the slider 103 are out of contact with each other, and the slider 103 is able to move smoothly.
If a bearing gap of an air bearing becomes too large, a problem arises in that the rigidity of bearing decreases and vibration is generated. If a bearing gap becomes too small, on the other hand, another problem arises in that the guide comes in contact with the slider and this makes it difficult to accomplish precise positioning, though the rigidity increases. Therefore, the air bearings are generally so assembled that a bearing gap between the guide and the slider becomes about several microns by using a precision instrument such as a precision shim and a dial gauge. However, it is very difficult to assemble the guide and the slider in such manner that the bearing gap becomes several microns, as much experience and skill are required, through trial and error, in performing the work and assembly. Therefore, the working efficiency is not good. Besides, long periods of time were required for assembling, causing an increase in the cost of production.